Catalytic Asymmetric syntheses Using Vitamin B_<12> as a Chiral Catalyst

使用维生素 B_<12> 作为手性催化剂的催化不对称合成

• 批准号: 61470092
• 负责人: OGOSHI Hisanobu
• 金额: $ 3.78万
• 依托单位: Technological University of Nagaoka
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1986
• 资助国家: 日本
• 起止时间: 1986 至 1987
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-61470092/
• 关键词: VITAMIN B_<12>; MICHAEL ADDITION; CYCLOPROPANES; ASYMMETRIC REDUCTION; 有機金属化合物; ビタミン【B_(12)】; 不斉合成触媒; 有機金属錯体

Vitamin B_<12> reacts with cyclopropanes having electron-withdrawing substituents such as acetyl, methoxycarbonyl, and cyano groups to give 3-substituted propyl-cobalt complexes. The alkylation with prochiral 1-acetyl-1-aklylcyclopropanes results in an asymmetric induction (ee 24-33%) at carbon 3 in the resulting alkyl ligands. Examination of the ^1H NMR spectra of the alkylation products indicates that (1) two prochiral methyl groups in 3,3-diacetylpropyl- and 3,3-bis(methoxycarbonyl)propyl-cobalt complexes are rendered diastereotopic by the presence of the chiral B_<12> and are observed to be spectroscopically nonequivalent and (2) enantiomeric methyl groups in 3-acetyl-3-alkylpropyl- and 3-acetyl- 3-(methoxycarbonyl)propyl-cobalt complexes having an asymmetric center at carbon 3 are also rendered diastereotopic and spectroscopically distinguishable in a similar manner.The Co-C derivatives thus obtained undergo photochemical homolysis to give Co(II) and alkyl radicals which abstract a hyrogen atom from isopropanol. Thus, B_<12> catalyzes the ring-cleavage reduction of cyclopropanes in 15% aq. NH_4 Cl-isopropanol (1:1) containg Zn dust under photochemical conditions. When 1-phenyl-1-methoxycarbonylcyclopropane is used as substrate substantial asymmetric reduction is observed. In the presence of Michael olefins (methyl acrylate, methacrylate, or crotonate), B_<12> also catalyzes the Michael addition of cyclopropane-derived C-3 unit. The mechanism involves (1) photochemical homolysis of a Co-C derivative to give Co(II) and an alkyl radical, (2) homolytic Michael addition of the radical to a Michael acceptor, (3) hydrogen abstraction of the resulting ardical from isopropanol, (4) Zn reduction of Co(II) to Co(I), and (5) reaction of Co(I) with the cyclopropane to regenerate Co-C derivative.

维生素B_<12>与具有吸电子取代基如乙酰基、甲氧羰基和氰基的环丙烷反应，得到3-取代的丙基-钴络合物。与前手性1-乙酰基-1-烷基环丙烷的烷基化导致在所得烷基配体中的碳3处的不对称诱导（ee 24-33%）。对烷基化产物的^H NMR光谱的检查表明：（1）3，3-二乙酰基丙基-和3，3-双（甲氧羰基）丙基-钴络合物中的两个前手性甲基由于手性B_的存在而呈现非对映异构体，<12>并且观察到在光谱上是不等价的，以及（2）3-乙酰基-3-烷基丙基-和3-乙酰基-3-烷基丙基-中的对映异构体甲基。（甲氧羰基）丙基-钴配合物在碳3上具有不对称中心，也以类似的方式呈现非对映异构性和光谱上可区分的。由此获得的Co-C衍生物进行光化学均裂，得到Co（II）和从异丙醇中夺取氢原子的烷基。因此，B_<12>催化环丙烷在15%水溶液中的开环还原。NH_4Cl-异丙醇（1：1）体系在光化学条件下对含锌粉尘的吸收。当1-苯基-1-甲氧羰基环丙烷用作底物时，观察到大量的不对称还原。在Michael烯烃（丙烯酸甲酯、甲基丙烯酸酯或巴豆酸酯）存在下，B_<12>还催化环丙烷衍生的C-3单元的Michael加成反应。其机理包括：（1）Co-C衍生物的光化学均裂，生成Co（II）和烷基自由基;（2）烷基自由基与Michael受体的均裂Michael加成;（3）烷基与异丙醇的夺氢;（4）Zn还原Co（II）生成Co（I）;（5）Co（I）与环丙烷反应生成Co-C衍生物。

项目成果

H,Ogoshi, Y,Kikuchi, T,Yamaguchi, H,Toi, Y,Aoyama: "Asymmetric Induction in the Nucleophilic Cyclopropane Ring Cleavage Reaction with Vitamin B_<12s>" @organometallic. 6. 2175-2178 (1987)

H，Ogoshi，Y，Kikuchi，T，Yamaguchi，H，Toi，Y，Aoyama：“维生素 B_<12s> 亲核环丙烷环裂解反应中的不对称诱导”@organometalic。

H.Ogoshi;K.Saita;T.Watanabe;H.Toi;Y.Aoyama: Tetrahedron Letters. 27. 6365-6368 (1986)

H.Ogoshi；K.Saita；T.Watanabe；H.Toi；Y.Aoyama：四面体字母。

H,Ogoshi, Y,Kikuchi, H,Ohnishi, H,Toi, Y,Aoyama: "Photochemical Three-Carbon Homologation of Michael Olefin with Cyclopropane Derivatives as Catalyzed by Vitamin B_<12>" Chem. Lett.

H，Ogoshi，Y，Kikuchi，H，Ohnishi，H，Toi，Y，Aoyama：“维生素 B_<12> 催化迈克尔烯烃与环丙烷衍生物的光化学三碳同系化”化学。

Y.Ozaki;T.Kitagawa;H.Ochiai;H.Ogoshi: J.Phys.Chem. 90. 6105-6118 (1986)

Y.Ozaki；T.Kitakawa；H.Ochiai；H.Ogoshi：J.Phys.Chem。

H. Ogoshi;Y. Kikuchi;T. Yamaguchi;H. Toi;Y. Aoyama: Organometallics. 6. 2175-2178 (1987)

H.大越；Y.